Effects of coronal plane conformity on tibial loading in TKA: a comparison of AGC© flat versus conforming...

Conforming articulations potentially decrease polyethylene contact stresses in total knee arthroplasty (TKA); however, less is known about the effect of coronal geometry on tibial loading and clinical failure. This study examined the relationship between coronal plane geometry and loading patterns in the proximal tibia. Composite tibiae were implanted with modular, metal-backed tibial trays and were compressively loaded with conforming and nonconforming ultra-high molecular weight polyethylene (UHMWPE) tibial bearings and comparable femoral components. Changes in strain on the proximal tibia were quantified using a photoelastic strain analysis method. In balanced loading, coronally dished components created a strain increase in the anterior medial tibia while creating a significant strain decrease in the posterior tibia. Proximal tibial strains were decreased and centralized in conforming versus flat articulations. This centralization of loading may lead to a reduction in edge loading during gait. Lower strains were observed with coronally dished implants in key regions corresponding to the clinical overload of the tibia leading to aseptic loosening.